Top drive systems are used to rotate a drill string made up of tubulars within a wellbore. Some top drives include a quill that provides vertical float between the top drive and the drill string, where the quill is usually threadedly connected to an upper end of a tubular of the drill string to transmit torque and rotary movement to the drill string. Alternatively, it may be indirectly linked to the drill string through a clamp, for example.
While drilling, drilling fluids or drilling mud are delivered to the drill string through a washpipe system connected to the quill. From the top drive and associated wash pipe, the fluids are transported and supplied to the drill string through the quill. Sometimes additional drilling fluids such as cement, chemicals, epoxy resins, etc. are also delivered downhole via the same system.
Conventional washpipes move axially and rotationally relative to surrounding support structure. A single seal is arranged to seal against the washpipe to prevent leakage of drilling fluid. Since the seal is subject to frictional movement in both the rotational and the axial directions, the seal wears quickly, requiring frequent replacement. Thus, drilling must be halted while the seal is replaced. This frequent downtime increases drilling expenses and slows the overall drilling progress.